Vehicles using the enhanced vortec V6 engine may be hard to start run poorly and/or use to much fuel due to a fuel leak inside the intake manifold plenum. Commonly this is caused by a leaking fuel pressure regulator or fuel line. The fuel system will need to be pressurized with the upper intake manifold removed in order to determine the exact cause of the leak. Removing the "tuning valve" from the upper intake can allow for limited visual inspection without removing the upper intake manifold.Google+
Car Problem Reports
Oldsmobile Bravada Engine Running Rich Due to Fuel Leak Inside Intake Manifold
Oldsmobile Bravada Problem
Visitor, 1992 Oldsmobile Bravada, 150,000 mi
Engine running very rich, about 7 miles to the gallon is all I get, carbon builds up, exhaust is very rich in fuel smell. Have tried different things so far nothing works, could it be a sensor, have replaced different ones, still nothing works.